N scale DCC and Blocks

[Flare]

Is there any concern if the bus wires touch or do they need to be separated a certain distance. 

My layout actually uses lamp wire for the bus, I don't have issues with cross-talk.

And the rails aren't spaced very far apart either, you shouldn't need to worry.

[Maletrain]

Flare,  I know the standard advice,which is to twist the bus wires about 3 turns per foot to avoid signal distortion and interference.  But, I really don't know how important that actually is for smallish layouts.  I know that NCE recommends that the cab bus and the track bus wires not be run close to each other to avoid cross-talk, even when twisted.  Those two buses are carrying different signal "traffic".   For a shelf layout, they recommend putting the cab bus along the front edge (so that it can have places to plug-in throttles) and the track power buses along the back edge.  That would seem to imply that the track power buses (that all carry the same DCC signals) can run parallel for whatever distance is needed to get a bus to a distant power district through another power district that is between the command station and the more distant track power district.

[Fish]

Working on installing bus and feeders.  I thought I would fire up the Power Cab, as per directions.  I also hooked the track wires into the power panel.  I had feeder wires  hooked up to one section of track.  However I was unable to detect any voltage.  So I checked voltage at the power panel wire "do-hicky" connector.  Again I was unable to detect any voltage from the track wire connection.  What am I missing regarding voltage? Is it possible the voltage meter will not read low voltages.  It only has 2 ranges, 700 and 200v.   I am using wire connectors from bus to feeders. The cab powered up as it should.  Power to the cab but not to the tracks. I will contact NCE tech support but maybe there is a simple fix or explanation other than it's defective.

[Flare]

Are you setting your tester for DC or AC?

DCC uses a digital wave form that mimics AC.

[Hunt]

System connected properly?
Looking at PCP (Power Cab Panel -  aka Power Panel)  with Red LED on bottom
Power Cab >>Flat cable >> left socket of the PCP(Power Cab Panel)

Voltage on track
Read using meter AC setting
Power output to track is full voltage PWM alternating DC waveform seen by meter as an AC waveform,  about 13.5 VAC , 5,000 to 8,500 Hz
Your meter set on AC is calibrated to read 60 Hz sine wave AC so you will not get an accurate reading.

[Fish]

Yes I am using the AC setting on the meter.  All plugs in proper place. The Cab is reading as per the manual.  I had placed a dcc on board diesel on the segment with feeder wires attached.  Initiated programming as per manual but got no indication of power to track.

Re Hunt comment:  You said my meter would get an inaccurate reading.  I am getting no reading.

[Hunt]

Fish,
When using Program Track (page 46, Power Cab System Reference Manual. Rev. 1.65) there is no voltage sent to track by Power Cab except for very brief moment a command is set to decoder. Your meter will never show this as time frame too short.

[Hunt]

*** edited ***

Fish,

When using Program Track (page 46, Power Cab System Reference Manual. Rev. 1.65) voltage to track is  turned OFF by Power Cab except for a very, very brief On  moment, then back OFF as a command is sent.   Meter does not display any track voltage when using programming track mode as time voltage is On is too short.

Can your meter display 12 to 13.5 volt AC?



Place a DCC equipped locomotive on track and turn on power to the Power Cab Panel. After the Power Cab system start up sequence is complete -- can you toggle locomotive headlight On and OFF by pressing HEADLIGHT button? If not, recheck all the wiring.

[Hunt]

Place a DCC equipped locomotive on track and turn on power to the Power Cab Panel. After the Power Cab system start up sequence is complete -- can you toggle locomotive headlight On and OFF by pressing HEADLIGHT button? If not, recheck all the wiring.

Fish........You do know --- you have to SELECT LOCO before you can turn its headlight On and Off

If not, follow Quick Start page 1 of the Power Cab System Reference Manual. Rev. 1.65

[Hunt]

In other words,
While not an accurate measurement a multimeter, even a cheap one like a Harbor Freight 7 Function Digital Multimeter  free one with coupon,  set on AC volts to read DCC track voltage can be used and is usually good enough. In fact it is more accurate reading DCC than some expensive True RMS multimeters.



The technical stuff
The commonly found multimeter is designed and calibrated to measure an AC sine waveform in the 50-60 Hertz range. DCC is not an AC sine waveform but an alternating DC (yes – DC) waveform containing digital information and is a higher frequency.   DCC is bipolar pulse-width modulation (PWM) DC (direct current)  waveform.

Image borrowed from Mark Gurries DCC website

[Fish]

My appreciation to those who have offered advice.  The problem has been corrected at least to the point of getting power to run my DCC ready loco as far as I have feeders connected.  I do have one of those HF "cheap" multi-meters but once I saw I had power checking track voltage became less important. To Hunt: mistake was my brain not registering what my eyes were seeing.  Once both of them were working together it was an easy fix. 

[Hunt]

. . . .  The problem has been corrected at least to the point of getting power to run my DCC ready loco as far as I have feeders connected. . . . .

What are you using to run the locomotive? A NCE Power Cab will not run a DCC ready locomotive.

DCC ready is short for 'DCC ready for a decoder to be installed.'

DCC Ready means the motor brushes are isolated from the power pickups and there is some means, a socket, solder pads, wires or something else, to accept the installation of a DCC decoder.

Another way to look at DCC ready - once a DCC decoder is installed the only electrical path to the motor is through the decoder.